#include <cctype>
#include <fstream>
#include <iostream>
using namespace std;

int main(int argc, char **argv)
{
    if (argc < 3)
    {
        cout << "Usage: " << argv[0] << " input_file output_file" << endl;
        return 0;
    }
    ifstream ifs(argv[1]);
    if (!ifs)
    {
        cerr << "can't open input file " << argv[1] << endl;
    }
    ofstream ofs(argv[2]);
    if (!ofs)
    {
        cerr << "can't open output file " << argv[2] << endl;
        return 1;
    }
    char c;
    while (ifs.get(c))
    {
        ofs << char(tolower(c));
    }
    return 0;
}